Detecting the BLAS and LAPACK math libraries

Many numerical codes rely heavily on matrix and vector operations. Think for example of matrix-vector and matrix-matrix products, the solution of linear system of equations, the calculation of eigenvalues and eigenvectors or singular-value decompositions. These operations might be so ubiquitous in the code base or might have to be run on such large data sets that the availability of efficient implementations becomes an absolute necessity in your code. Fortunately, there are libraries just for that: the basic linear algebra subprograms (BLAS) and the linear algebra package (LAPACK) offer standard APIs for many tasks involving linear algebraic manipulations. Different vendors provide different implementations, but all of them share the same API. While the actual programming languages for the underlying implementation of the math libraries varied over time (Fortran, C, Assembly), the remaining historical trace is the Fortran calling convention. Our task in this recipe will be to link against these libraries and show how to seamlessly work with a library written in a different language, considering the above-mentioned calling convention.